Millimeter wave signals are used for radar and telecommunications. They are also capable of being used to produce an image of a subject by directing millimeter-wave signals at the subject and detecting the reflected signal. Examples of such imaging systems have been described in U.S. Pat. Nos. 5,455,590; 5,557,283; 5,859,609; and 6,507,309; and U.S. patent application Ser. No. 10/607,552 filed Jun. 26, 2003; U.S. patent application Ser. No. 10/697,848 filed Oct. 30, 2003; U.S. patent application Ser. No. 10/301,522 filed Nov. 21, 2002; and U.S. patent application Ser. No. 10/697,965 filed Oct. 30, 2003 which patent references are incorporated herein by reference.
When imaging systems are used for surveillance of persons in a security system, the safety of the facilities and patrons of the facility for which the surveillance is being conducted may depend on the effectiveness of the system. The imaging of persons subjected to surveillance may be more willing to allow the surveillance if it is performed in a manner that protects the person's privacy. This is particularly true in situations where the surveillance delays the intended progress of the person or persons being surveilled, such as prior to boarding a public transportation vehicle, or prior to entering a public or protected facility.